Random orbital buffing devices are well known in the art. They are used to polish and finish various surfaces without the drawbacks inherent to rotary-type buffing devices. For example, a random orbital buffer may be used to polish a coat of paint on a new automobile. Random orbital buffing devices are commonly pneumatically-powered. After being used to power the device, the compressed air or gas must be exhausted from the device. One problem common to pneumatic devices is that the exhausting air may produce a large amount of noise, which is undesirable for the user of the device.
For example, abrading tool 10 is shown in FIGS. 1A and 1B. Tool 10 includes head 12, which houses a drive means for driving abrasive pad 14. The drive means may be, for example, a drive means according to U.S. Pat. No. 6,206,771 (Lehman) or U.S. Pat. No. 4,854,085 (Huber et al.), which patents are incorporated herein by reference. Head 12 is affixed to handle portion 16, which includes trigger mechanism 18 for controlling the operation of tool 10. Port 20 is located at the back of the handle portion for coupling the tool to a pneumatic power source, such as a pressurized air tank. Shroud 22 is included to at least partially contain the drive means. Hang ring 24 may be included to provide a convenient means for storing the device when not in use, such as from a hook.
Many devices incorporate mufflers to reduce the noise produced by the exhausting air. Traditionally, these mufflers increase the overall size of the device. To reduce the negative effects that this extra size has on the device's usability, these mufflers are commonly placed in or attached to the device's handle, since there is no room to accommodate a muffler in the head portion of the tool proximate the drive means. The channel from the coupling port (port 20) for the input air is frequently in the handle for the same reason, leading to a common design where the input and exhaust air lines are coaxial or parallel to each other in the handle of the device. That is, separate input and exhaust channels are both included in the handle.
For example, muffler 26 is included at the rear of tool 10 to muffle the exhaust of the device. This embodiment results in the exhaust air being vented from the rear of the device, near the connector for the input air. This embodiment adds complexity to the device in the form of a second air line that runs the length of the device between the muffler and the outlet of the drive means. Additionally, a constant current of air is exhausted near the user while the device is in use.
An alternative to this embodiment is included in some grinding devices, which involves venting the exhaust air from the front of the device, onto the abrading pad. Directly exhausting the drive means onto the abrading pad advantageously provides cooling of the pad. Additionally, two separate lines or channels are not required in the handle portion, reducing the complexity of the handle. Also, this eliminates the need to include a muffler, which, in addition to the lack of two channels in the handle, enables more design choices in handle shape and size.
However, internal space is very limited in the head of these tools, resulting in front-exhaust tools which do not include mufflers. For grinding operations, muffling the exhaust is not a necessity, due to the inherent loudness of grinding. However, muffling is vital for buffing tools to reduce the noise of the tool. Thus, front-exhausting tools tend to be much louder than rear-exhausting tools. Some embodiments attempt to combine the benefits of the front-exhausting and rear-exhausting embodiments by piping the exhaust air from the muffler at the rear of the handle of the device with an exterior line to carry the exhaust back to the front of the device, where it is exhausted onto the pad. This embodiment adds the extra complexity and size for the exterior exhaust line.
A final problem common to pneumatically-powered buffing devices, and buffing devices generally, is that heat created by the buffing action can damage the surface that is being polished. To prevent the build-up of excess heat, buffing devices are usually limited in speed, or users must operate the devices carefully to ensure particular portions of the surface are not overworked. These limitations reduce the effectiveness of the device, increasing the time needed to polish the surface.
As can be derived from the variety of devices and methods directed at effectively exhausting pneumatically-powered buffing devices, many means have been contemplated to accomplish the desired end, i.e., preventing the exhausting air from interfering with the buffing action of the device. Heretofore, tradeoffs between noise, device design, preservation of the surface to be polished, and user comfort were required. Thus, there is a long-felt need for a pneumatically-powered buffing device that minimizes exhaust noise and accidental damage to the surface to be polished, while preventing the device's exhaust structures from interfering with the timely and efficient operation of the device.